Review of Medtronic Pumps & CGM

Medtronic 770G/670G: Best Insulin Pump + CGM for Me?

How do you choose the best insulin pump for you, or for your child? The key is finding the one with the key features that match YOUR family's needs and lifestyle - while also avoiding your personal deal-breakers. We break it down for you here by presenting a concise summary and clear details (including the pros and cons) of Medtronic Minimed™ 770G, 670G, and 630G Insulin Pump + CGM Systems, as well as the Guardian Connect stand-alone CGM.

NOTE: This independent review is provided by Waltzing the Dragon; we are not affiliated with Medtronic Diabetes Canada. For sales enquiries, please contact Medtronic directly.

Medtronic Canada offers four separate insulin pump and/or CGM systems right now:

1. Minimed™770G Hybrid Closed-Loop System (approved in Canada in December, 2020 and NOW AVAILABLE), with some automatic insulin adjustment features for both highs and lows, PLUS (new to 770g) Bluetooth connectivity, and access to future software updates.

Medtronic Minimed 770G insulin pump

2. Minimed™670G Hybrid Closed-Loop Insulin Pump/CGM System (released in Canada in December, 2018), with some automatic insulin adjustment features for both highs and lows.

 

3. Minimed™ 630G Insulin Pump/CGM System (released in Canada in April, 2017), an integrated system which shuts off basal insulin delivery automatically when your glucose reading is low.

4. Guardian™ Connect CGM, a stand-alone glucose monitoring system for those who prefer to deliver insulin via injections, or who pump their insulin using a separate pump.

For a side-by-side comparison of these systems, plus those by other manufacturers:

What's New with the Minimed 770G?

The Minimed 770G is Medtronic's newest pump/CGM system to be approved in Canada. It has many of the same features of the 670G, including automatic insulin adjustment, predictive technology to prevent lows, CGM trend info and alerts, and a large capacity insulin cartridge. It uses the same sensor as the 670G (Guardian Sensor 3), and the same algorithm to respond to glucose readings.

Plus the 770G offers some handy features, new to Medtronic users:

  • the 770G is approved for those with type 1 diabetes ages 2 and up, the only Hybrid Closed Loop system currently available in Canada for children under 6 years old.

  • the ability to access future upgrades for your pump via a software upload, without having to replace the pump itself. This means that when new features become available, you won't have to wait 4 years to get access to them, you will simply download the software upgrade to the existing hardware. (This upgradability is also available with the Tandem t:slim.)

  • smartphone connectivity, which gives you the option of using your smartphone (both iOS and Android) as a secondary CGM receiver, and which also allows for remote viewing of CGM data. (This feature is also available with other glucose monitoring systems.)

Remote Viewing of Glucose Data

  • If you would like to keep an eye on your child's BG while they are away from you at school, at a friend's house, or at gymnastics practice, Medtronic offers two options:

    • the Minimed 770G (integrated pump and CGM) with smartphone connectivity allows remote viewing of CGM data, as does...
    • the stand-alone Guardian Connect CGM, which offers an interface for up to 5 users via a compatible smartphone. You can stay connected to your loved ones with the CareLink™ Connect platform, which includes anytime access to glucose data, as well as automated text message alerts.

(The other system currently available in Canada that allows for remote viewing of CGM data is the Dexcom G6, available as either a stand-alone or integrated system.)

Key Features of Medtronic Pump/CGM systems:

Integrated or Stand-Alone?

Medtronic offers both stand-alone CGM systems, as well as those integrated with an insulin pump.

  • If you’re looking for an insulin pump system with integrated Continuous Glucose Monitor (CGM), all three Minimed insulin pumps (770G, 670G and 630G) fit the bill, representing three of the four integrated pump/CGM systems currently available here in Canada. (Tandem t:slim with Dexcom G6 is the other.)

    What do we mean by “integrated”? The two parts – pump and CGM – work together within a single system: you can see your glucose data on the pump screen; the CGM communicates glucose data to the pump, pre-populating the bolus function so that you don’t have to manually enter your reading to correct a high.

  • The 770G and 670G give you the most flexibility in how you manage diabetes. It's like having 3 systems in one:

    1. You can use the integrated system in full Auto Mode, where insulin is automatically adjusted for both highs and lows. Or...
    2. You can use it in manual mode, as a typical insulin pump with no automation, giving you control over adjusting insulin and reacting to highs and lows. This is particularly useful if you don’t want to use CGM full-time. Or...
    3. You can run it somewhere in between, as an integrated pump+CGM system with some automatic insulin adjustment to prevent lows, such as Suspend Before Low. This would essentially be the same as the Minimed 630G.
  • If you’re looking for glucose monitoring options that are independent of a particular insulin pump, then consider the stand-alone Guardian Connect CGM system, which gives you the freedom to use it without a pump, or independently alongside any pump. If you're happy on Multiple daily Injections (MDI) but would like to add CGM as a glucose monitoring tool for better management, then this stand-alone fits right in. In addition, if you want to use your smartphone as the receiver, the Guardian Connect takes sensor glucose readings every 5 minutes, and uses smart technology to predict when you're going too high or low, sending the notification to your phone.

    (You may also want to include in your research the other stand-alone glucose monitoring systems currently available in Canada: Dexcom G6 Continuous Glucose Monitor; Freestyle Libre and Libre 2 Flash Glucose Monitors.)

Automatic Insulin Adjustment

Auto Insulin Adjustment is one of the latest and greatest features of insulin pumps, truly giving me hope for the future of T1D treatment, and for my son's ability to cope with all the demands of daily diabetes care.

The Minimed 770G and 670G models are Hybrid Closed Loop systems. Although other such systems are available (like the t:slim X2 with Control-IQ), the Medtronic 670G was the first to market.

What does “Hybrid Closed Loop” mean? In short, the pump and CGM portions of the system are not just “integrated”, but the pump actually reacts to the information communicated from the CGM: in AUTO mode, the pump automatically adjusts your basal (background) insulin – up or down - every 5 minutes based on the glucose readings from the CGM. When glucose rises, background insulin is increased; when glucose drops, background insulin is decreased as needed. To prevent low glucose, the system shuts off basal insulin when glucose is low. The goal is to increase your time in-target so that both lows and highs are reduced, through the day and night. (Sleep-deprived parents, take heart!)

Why “Hybrid”? This term refers to the fact that the system is not fully automated. In a true closed loop system you would “set it and forget it”, and the system would take action with minimal user input. In a hybrid closed-loop system, however, user input is still required: For example, for meals you need to check glucose, enter the carb amount in the food you are about to eat, and then accept the bolus recommendation as calculated by the system.

Check out this video on the automated features of the Minimed 670G.

Note that the Medtronic pumps currently available in Canada only adjust basal insulin, not bolus insulin; the insulin dose that you deliver for food or to correct an existing high will NOT be adjusted automatically by the 770G. However, the Minimed 780G (available in Europe now, pending approval in the US, but not currently available in Canada) also provides a correction bolus to help lower above-target glucose, as does the Tandem t:slim X2 with Dexcom G6 integration. 

Also be aware that auto basal adjustment will not eliminate lows (or highs) entirely - all the usual culprits (exercise, too much insulin, inaccurate carb-counting, stress, etc.) may impact blood glucose more, or more quickly, than a change in basal insulin is able to cover. But still, the technology goes a long way to help lift the burden of daily diabetes care.

Suspend on Low feature

One example of automatic insulin adjustment is a feature called Suspend on Low, available on all Minimed pumps (770G, 670G and 630G), which will stop basal insulin delivery when glucose is low. It works like this: when glucose drops below a set threshold, the system alerts you; if you do not acknowledge that Low Alert with a button press, it will suspend basal insulin delivery, giving your glucose time to rise. So if you are asleep during a hypoglycemic episode, or if you are awake but are unable to respond (experiencing a severe low blood sugar, for example) then you will not continue to receive insulin which would compound the low. When basal insulin delivery will automatically resume depends on the particular model: the 770G and 670G will automatically resume when glucose rises; the 630G will automatically resume after 2 hours.

At first glance an interruption in basal insulin delivery may not seem like a good idea, as it may lead to high glucose a few hours later. However, when a user may not otherwise be able to deal with the low, the benefits outweigh the drawbacks. Also, with basal insulin resuming with a rise in glucose (770G, 670G), the rebound effect is minimized, so glucose stays in range more.

Predictive Technology

If you want a bit more of a heads up when you might be headed for a low, then you’ll may be interested in the predictive features of the Minimed 770G/670G/630G:

  • Alert Before Low / Alert Before High notifies you when the system predicts that glucose will go low (or high) within the next 30 minutes (for the 770G, 670G, and 630G) or within the next hour (for the Guardian Connect). With the 770G & 670G, insulin will be adjusted automatically to try to avoid the low (see the next point, Suspend Before Low); with the 630G and Guardian Connect, insulin delivery won't change, but the advanced notice gives you a chance to take action to potentially avoid the low (by eating extra carbs or manually changing insulin delivery).

  • Suspend Before Low (770G & 670G) takes this “heads up” one step further by stopping basal insulin up to 30 minutes before reaching your preset low limit, then automatically restarting it when your glucose levels recover. The goal of the Suspend Before Low feature is to help avoid lows and their subsequent rebound highs.

Tips from the Trenches

Our son only uses CGM part-time, to give us insight into glucose trends and to tweak insulin doses periodically; he doesn’t use it full-time because he has relatively little “real estate” and because we get Alert Fatigue when he wears CGM. Other families only use CGM intermittently to manage the cost of sensors. Sometimes pumpers just want to reduce the tech burden by taking a break from their CGM. In all of these cases, you could still use the 670G, but you wouldn’t have access to the glucose alerts or automatic insulin adjustment. ~Michelle

More Time on Target

  • The 770G & 670G focus on Time In Range as the main metric; more successful management is indicated by more of your readings falling within the upper and lower ends of your glucose goals (between 4 and 7 mmol/L, as one example). The company reports an average of 2% Time in Range within a controlled clinical trial environment4, and 70.7% Time in Range when the 670G system is used in the real world5… that’s amazing!

    To temper our excitement to a reasonable amount, we need to remember that the validity of Time In Range - or any other metric - as a measure of how effectively glucose is being managed depends on the accuracy of the system; in this case, on the accuracy of the CGM sensor.

    Let me illustrate with a hypothetical example:

    If the data generated from my d-device says that my glucose is between 4 and 7 mmol/L 100% of the time, but the d-device is wrong 50% of the time, then I’m actually only in-range 50% of the time (not 100%, like the system says).

    This is an extreme example, as no system will say you’re in-range 100% of the time, and accuracy rates for glucose monitoring systems (from CGM to Flash to BG meters) are typically below 15% (much more accurate than 50%). However, the point remains that accuracy must be considered when interpreting glucose data from any diabetes technology.

Stored Data

  • The 770G and 670G use the newer Guardian Link 3 Transmitter, while the 630G uses the “Guardian” CGM transmitter, both of which have significant internal data storage: the transmitter itself stores up to 10 hours of glucose data.

    What this means for real life is that if you disconnect from your pump to go swimming, or you leave the pump in the locker room for an hour while you work out, or you take a 9-hour flight across the Atlantic and put the pump in airplane mode for the entire flight… at end of the swim, workout or flight, all of the data is transferred from the transmitter to the receiver, without a gap in data. (Note that if you have disconnected for less than 6 hours, the transmitter and receiver will automatically reconnect; if it’s been longer than that you’ll need to manually reconnect them.)

CGM Alerts

  • All 3 systems include the Low Alert and High Alert features common to CGM systems (called Alert on Low or Alert on High by Medtronic).

Glucose Trends

  • Like other CGM systems, all four Medtronic systems provide glucose trend information. Up or down arrows tell you if your child’s glucose is rising or falling, and how fast; a horizontal arrow tells you that glucose is steady (not changing significantly):

    ↓  or ↑   Single arrow down/up means that glucose is falling/rising at a rate of 1-2 mmol/L over 20 mins

    ↓↓  or ↑↑   Double arrows down/up means that glucose is falling/rising at a rate of 2-3 mmol/L over 20 mins

    ↓↓↓  or ↑↑↑ Triple arrows down/up means that glucose is falling/rising at a rate of more than 3 mmol/L over 20 mins

    This glucose trend information allows you take action based on how your child’s glucose is changing – and how fast it’s changing. After all, 7.0 mmol/L with ↓ is quite different from 7.0 mmol/L with ↓↓↓!

Meters & Remotes

  • Both the 630G and 670G systems (770G TBD) include a linked Contour®Next blood glucose meter, which sends glucose readings wirelessly to the insulin pump, saving time and effort, as well as eliminating manual data entry errors.

    The meter can also be used as a remote to deliver a manual bolus, or one out of 8 preset bolus amounts (in units of insulin). So if your child has the same snack at school every day, she can simply select that preset program to deliver the correct amount of insulin for that snack. Or if you’re in the drive-through at Tim Horton’s with your child strapped in the car seat in the back, you can use the remote from the front seat to deliver the preset amount that corresponds to a Vanilla Dip.

    (If you’re looking for a remote that includes a bolus calculator, so that you can enter the amount of carbs and let the remote calculate and deliver the correct amount of insulin, this meter won’t fit the bill; the linked BG meter does not include Bolus Wizard, which can only be accessed on the pump itself. In Canada right now, the only fully functional meter-remote for an insulin pump is the Omnipod PDM.)

Can I swim with my Medtronic pump or CGM?

  • All three pumps (770G, 670G, and 630G), which also act as the CGM receiver, are fully water-proof, with an IPX8 rating (= waterproof when submerged up to 3.6m (12 ft.) for up to 24 hours). So you can go ahead and swim, shower, bathe, exercise, and sweat while wearing your pump.

    The CGM transmitter (which clicks into the sensor and is worn on your belly, buttocks, arm, etc) has a different rating than the pump body/CGM receiver; it’s waterproof up to 2.4 meters (8 feet) for up to 30 minutes.

Lots of Room for Insulin

  • All three pump models (770G, 670G, 630G) have a large capacity insulin reservoir that holds up to 300 units of insulin.

Tips from the Trenches

When purchasing a pump for a 10 year old you cannot imagine needing more than 180 units over three days but by the time the warranty is up on the pump your 10-year-old is now 14, the size of a grown man and in the throes of puberty, using 100+ units of insulin a day.  The 300 unit reservoir was invaluable for our family when our son’s insulin needs increased dramatically!  Even before this happens, you do not have to fill the reservoirs – just put enough insulin in for three days and enough extra for priming out any air bubbles.
-Jacky, mom of a 13-year-old boy with type 1 diabetes

You Can't Quit Your Job as a Pancreas Yet

  • Compared to some other systems, the Medtronic hybrid closed loop systems seem to require a fair amount of user input to take advantage of the automated features. For example, if your glucose reading rises above 13 mmol/L for a period of time, the 670G will require you to input the result of a fingerstick BG check; if you don’t enter one, the system will shut off automated features, reverting back to a manual pump. This may result in more fingerstick checks than with other integrated pump/CGM systems.

    In addition, the 670G is missing some key features that some pumpers have come to rely on (like Extended Bolus and Temp Basal). Although the automatic insulin adjustment is designed to eliminate the need for these features, the conservative algorithm may not be sensitive enough to accommodate for exercise, slow-digesting foods or high fat foods that traditionally require an extended bolus or temporary basal rate.

    In terms of personal experience with Auto Mode... you may find this commentary helpful, from Gary Scheiner in his review of (the US version of) the 670G.

Hold onto that Blood Glucose Meter

Fingerstick calibration twice each day is recommended for Medtronic CGM systems.

Medtronic Infusion Sets

  • As with all insulin pumps available in Canada, the tubing-to-reservoir connections are proprietary – if you have a Medtronic pump, only Medtronic infusion sets are compatible. According to the company, venting is used to maintain the proper pressurized environment for the pump mechanisms; this venting mechanism is built directly into the infusion set connection, so new venting is provided with each set change to help maintain the reliability of insulin delivery.

Sensor Life & Accuracy

  • The 770G, 670G and Guardian Connect (stand-alone CGM) all use the same sensor (Guardian Sensor 3) to detect the glucose levels in the interstitial fluid at the sensor site. The Medtronic website notes that: “The Guardian Sensor (3) glucose values are not intended to be used directly for making therapy adjustments, but rather to provide an indication of when a fingerstick may be required.” This sensor has an overall Mean Relative Difference (MARD*) of 11.2% for Adolescents and 10.0% for Adults1 across all blood glucose levels.

    *MARD = Mean Absolute Relative Difference, a measure of error (as an average %). MARD represents the difference between the patient’s CGM readings and the glucose values obtained from a lab analyzer. A lower value means values are closer to the lab reference value; that is, the sensor is more accurate than one with higher MARD values.

    (Calling all fellow data nerds! See The Data Behind Guardian Sensor 3 Accuracy at the bottom of this page for accuracy measures broken down by glucose level, and by day vs. night.)

    Each Guardian Sensor 3 is approved for up to 7 consecutive days of use.

  • The 630G uses a previous version, the enhanced Second Generation Enlite® Sensor, which the company reports has an overall Mean Relative Difference (MARD) of 13.0%2, 3.

    Each Enlite sensor is approved for up to 6 consecutive days of use.

For a side-by-side accuracy comparison of all systems:

Warranty

  • All three models (770G, 670G and 630G) have a 4 year warranty on the insulin pump/CGM receiver (plus up to 1 additional year under Medtronic’s Continuation of Therapy program, if insurance coverage will not allow you to replace the pump at 4 years - contact Medtronic for details).

  • There is a 5-year warranty for pumps obtained through a provincial insulin pump funding program, where a new pump is covered only every 5 years.

  • The CGM transmitter is covered by a 1-year warranty.

For a side-by-side accuracy comparison of all systems:

The Data Behind Guardian Sensor 3 Accuracy

If you're interested in diving a little deeper into the data, here it is...

Results of Research Study, Comparing venous samples (i-STAT) and sensor glucose (SG) for the Guardian Sensor 3 (used by the Minimed 670G CGM)1:

Time in Range:

  • Adults:

    Proportion of in-target glucose values during the hotel stay (controlled clinical trial environment): 74.2% (– 17.5%) for i-STAT venous samples; 76.9% (– 8.3%) for SG measurements, both of which were relatively comparable to the…

    Proportion of adult in-target SG values during the entire in-home study at 73.8% (– 8.4%).

  • Adolescents:

    Proportion of in-target glucose values during the hotel stay: 67.4% (–Standard Deviation (SD) of 27.7%) when assessed by i-STAT venous samples; 72.0% (– SD 11.6%) for SG measurements.

    Proportion of adolescent in-target SG values during the entire in-home study: 67.2% (– 8.2%).

    The lower percent of in-target values observed in adolescents relative to adults is not unexpected and likely due to higher activity levels and eating.

Sensor Accuracy (as measured by the MARD– SD between SG and i-STAT venous blood glucose values) during the hotel stay:

  • Overall sensor accuracy:

    11.2% (– 9.7%) for adolescents;

    10.0% (– 8.7%) for adults

  • Sensor accuracy within the target range (71–180 mg/dL =~3.9–10.0 mmol/L):

    10.5% (– 9.7%) for adolescents;

    9.6% (– 8.3%) for adults.

  • Sensor accuracy in the High Glucose range (>180 mg/dL = >~10.0 mmol/L):

    12.8% (– 9.1%) for adolescents;

    10.3% (– 7.8%) for adults.

  • Sensor accuracy in the Low Glucose range (<70 mg/dL = <~3.9 mmol/L):

    12.3 (– 9.2 mg/dL) for adolescents;

    12.2 (– 10.6 mg/dL) for adults.

  • By time of day:

    Overall daytime (from 7:00 a.m. to 10:00 p.m.) MARD: 10.4% (– 9.7%).

    Overall night-time (between 10:00 p.m. and 7:00 a.m.) MARD: 10.2% (– 8.3%).

References:

  • 1.

    Garg, S. K., Weinzimer, S. A., Tamborlane, W. V., Buckingham, B. A., Bode, B. W., Bailey, T. S., Brazg, R. L., Ilany, J., Slover, R. H., Anderson, S. M., Bergenstal, R. M., Grosman, B., Roy, A., Cordero, T. L., Shin, J., Lee, S. W., … Kaufman, F. R. (2017). Glucose Outcomes with the In-Home Use of a Hybrid Closed-Loop Insulin Delivery System in Adolescents and Adults with Type 1 Diabetes. Diabetes technology & therapeutics, 19(3), 155-163.

  • 2.

    Veeze HJ. et al Poster 136 ISPAD 2014 : Real-life performance evaluation of the New Generation Enlite™ glucose sensor in patients with Diabetes Mellitus.

  • 3.

    Enlite™ Sensor Performance Addendum, Paradigm® Veo™ Algorithm, True Alert Rate for Predicative and Threshold for 3.89 mmol/L @ 30 minutes; CLSI Guidelines, Method 2.

  • 4.

    Bergenstal R, Garg S, Weinzimer S, et al. Safety of a hybrid closed-loop insulin delivery system in patients with type 1 diabetes. JAMA. 2016;316(13):1407–1408. Actual results are based on clinical trial. Time in range results reported in pivotal trial were measured from 71-180 mg/dL (3.9-10.0 mmol/L).

  • 5.

    Agrawal, Pratik & Stone, Michael & Gopalakrishnan, Shweta & Fogel, Catherine & W. Lee, Scott & R. Kaufman, Francine. (2018). Real-World Data from the MiniMed ™ 670G System Commercial Launch. Diabetes Jul 2018, 67 (Supplement 1) 960-P; DOI: 10.2337/db18-960-P.